Back-End Developer interview questions: the 8 to ask

1. 1.How do you design a versioned API?
2. 2.How do you keep data consistent across two services?
3. 3.How do you choose a database index?
4. 4.How do you protect an API from abuse?
5. 5.How do you make an operation idempotent?
6. 6.Which caching strategy would you use, and how do you invalidate it?
7. 7.How do you measure a service's health in production?
8. 8.Tell me about an architecture decision you regret.

Tip: for every answer, ask for a concrete example (situation, action, result). An answer without an example is worth half.